# Sound and Vibration Basics

## Leq - Equivalent Continuous Sound Level - LAeq

### Leq Definition

### Leq is the preferred method to describe Sound Levels that vary over time, resulting in a single decibel value which takes into account the total Sound Energy over the period of time of interest..

### Leq - equivalent continuous noise level :

Noise levels often fluctuate over a wide range with time. For example in the middle of the night the level might go down as low as 30dB(A) with occasional passing vehicles of 70dB(A) or more. Later comes the dawn chorus followed by the general noises of the day before relative peace returns in the late evening.### LAeq - It is common practice to measure noise levels using the A-weighting setting built into all sound level meters. In which case the term is properly known as LAeq and the results should say so - for example LAeq = 73 dB or Leq = 73 dBA

### Leq noise levels

are Logarithmic (dB) values and cannot be added directly. A doubling of sound level results in a measured increase of 3 dB, four identical sources in a room would increase the noise level by 6 dB and so on. This works both ways, say 10 similar machines in a room produce 100 dBA then removing one machine completely will only reduce the overall noise level to 0.5 dBA, you would need to silence or remove 50% of the machines to achieve a 3 dB reduction. See also our dB page for more details on adding and subtracting decibels - Leq Calculation.### LAT

: the time averaged level, specified in the IEC 61672 Standard, is the same quantity. However the Leq term is in common use.### Short Leq

: the preferred modern method of storing sound levels and displaying the true time history of a noise event. The resulting 'time histories', typically measured in 1/8 second intervals may be used to calculate the 'overall' levels for any sub-period of the overall measurement time.**see also :**Exponential Averaging l Linear Averaging l Statistical Noise Levels Ln, L10, L90% etc

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